The effects of antineoplastic agents on lymphocytes from peripheral blood in vivo will be measured by an analysis of DNA distribution patterns of Feulgen stained nuclei. The distribution patterns will be obtained by high resolution scanning microphotometry. Digitized cell images will be processed by computer to determine image parameters which have been found to lend themselves as sensitive indicators of the effects of antineoplastic agents. In particular, parameters derived from the correlation between certain optical density values are excellent measures of trends in the DNA distribution patterns. The agents to be examined are 5-fluorodesoxyuridine, 6- mercaptopurine, and methotrexate, as examples of antimetabolites, Melphalan as an alkylating agent, and prednisone, an adreno corticosteroid. The methodology will be developed in lymphocytes collected from guinea pigs, and hamsters, and will then be extended to peripheral blood lymphocytes collected from pre- and postoperative patients undergoing antineoplastic chemotherapy, and from patients with lymphocytic leukemia. It is the objective of the proposed research to develop a sensitive monitoring method for the response to chemotherapeutic treatment in vivo, at the cellular level.